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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 13 |
| 4 | 42 |
| 5 | 146 |
| 6 | 520 |
| 7 | 1893 |
| 8 | 6928 |
| 9 | 25520 |
| 10 | 95258 |
| 11 | 357332 |
| 12 | 1348314 |
| 13 | 5109674 |
| 14 | 19419422 |
| 15 | 74124571 |
| 16 | 283750244 |
| 17 | 1089053340 |
| 18 | 4189218564 |
| 19 | 16143369610 |
| 20 | 62342218516 |
| 21 | 241154261642 |
| 22 | 934254937426 |
| 23 | 3624326380994 |
| 24 | 14076738707662 |
| 25 | 54742699821140 |
| 26 | 213116870712502 |
| 27 | 830503102890218 |
| 28 | 3239368922556944 |
[1,1,4,13,42,146,520,1893,6928,25520,95258,357332, 1348314,5109674,19419422,74124571,283750244, 1089053340,4189218564,16143369610,62342218516, 241154261642,934254937426,3624326380994, 14076738707662,54742699821140,213116870712502, 830503102890218,3239368922556944] |